Dec 032013


Speaker: Xingyu Han

Title : The impact of fading on cross-layer packet-based design with single user &single channel


The research focuses on cross-layer (between network and physical layer) packet-based design with single user and single channel. The cross-layer analysis, using an M/D/s(t)/K queue model, applies Poisson packet arrivals to a finite buffer at network layer and automatic modulation and coding (AMC) schemes at physical layer. The cross-layer analysis is packet-based and operates on a slot-by-slot basis. The research validates M/D/s(t)/K cross-layer model which utilizes 6 modulation & coding schemes (MCS) at physical layer. The research analyses the impact of fading on cross-layer M/D/s(t)/K model compared to the M/D/1/K vacation model without fading, and shows that when the system load is high enough (usually above 0.8), the probability for queue length and packet drop probability (PDP) are such that the impact of different fading channels becomes negligible.

Furthermore, when there are multiple users waiting to be transmitted, we should decide which user is scheduled during each slot. The scheduling policies are used for accomplishing this task. The research also gives a basic explanation of a candidate proportional fairness (PF) packet scheduling policy, including MaxWeight, Exp-rule and Log-rule, and a primary analysis on how PF policies trade off between throughput and fairness. In addition, the research validates that log-rule policy optimises average scheduling delay for each user compared to MaxWeight and Exp-rule policies which optimise delay for the worst user.

Date: 4th  December, 2013.

Time: 14.00-15.00 hrs

Venue:  QMUL Maths:1.03

 Posted by on December 3, 2013